While not limited thereto in its utility, the present invention is particularly useful in the packaging of consumer products and particularly products which are packaged within a wrapper comprised of paper. Such packages, cigarette packets for example, are frequently provided with a thin transparent outer wrapping which may be opened by pulling on a tear strip. This outer wrapping may be comprised of cellophane. In the course of forming the package a tear strip is mated with a moving web of cellophane film, the tear strip and film then being welded together to form a wrapper which is thereafter used to envelope the cigarette packet or other package.
The mating of two moving webs, i.e., a packaging film and a tear strip, presents problems of long-standing in the art. Any departure from synchronism will produce curling and shrinkage during the welding of the tear strip to the packaging film. Such departures from synchronous movement are particularly likely to occur during starting and braking or stopping of the downstream packaging machine because there is a tendency to stretch the tear strip during such speed changes. The foregoing is also true when the supply speed of the packaging film and tear strip must be changed to accommodate the mode of operation of the packaging machine.